Chap. VIII. 
STEKILITY. 
249 
that close interbreeding lessens fertility, and, on the 
other hand, that an occasional cross with a distinct in¬ 
dividual or variety increases fertility, that I cannot doubt 
the correctness of this almost universal belief amongst 
breeders. Hybrids are seldom raised by experimen¬ 
talists in great numbers; and as the parent-species, or 
other allied hybrids, generally grow in the same garden, 
the visits of insects must be carefully prevented during 
the flowering season: hence hybrids will generally be 
fertilised during each generation by their own indi¬ 
vidual pollen; and I am convinced that this would be 
injurious to their fertility, already lessened by their 
hybrid origin. I am strengthened in this conviction 
by a remarkable statement repeatedly made by 
Gartner, namely, that if even the less fertile hybrids 
be artificially fertilised with hybrid pollen of the same 
kind, their fertility, notwithstanding the frequent ill 
effects of manipulation, sometimes decidedly increases, 
and goes on increasing. Now, in artificial fertilisation 
pollen is as often taken by chance (as I know from my 
own experience) from the anthers of another flower, as 
from the anthers of the flower itself which is to be 
fertilised; so that a cross between two flowers, though 
probably on the same plant, would be thus effected. 
Moreover, whenever complicated experiments are in 
progress, so careful an observer as Gartner would have 
castrated his hybrids, and this would have insured in 
each generation a cross with a pollen from a distinct 
flower, either from the same plant or from another plant 
of the same hybrid nature. And thus, the strange fact of 
the increase of fertility in the successive generations of 
artificially fertilised hybrids may, I believe, be accounted 
for by close interbreeding having been avoided. 
Now let us turn to the results arrived at by the third 
most experienced hybridiser, namely, the Hon. and 
M 3 
